Most people feel sleepy, grumpy, or dopey when they haven’t gotten enough hours of sleep. A new study in the Journal of Behavior Therapy and Experimental Psychiatry puts forth a theory on why sometimes less sleep can also lead us to be more depression-y and anxious-y. Their research takes aim at a common symptom of those conditions known as repetitive negative thoughts (RNT), which is basically your mind being a jerk and not letting you stop thinking about bad things. Using eye-tracking technology, they showed volunteers positive, negative, and neutral images, and found that volunteers fixated on the negative images longer and more intensely than the neutral and positive ones. They blame a lack of cognitive resources caused by not enough sleep for their inability to filter negative thoughts.